Cellobiuronic acid, the basic structural unit of Type III pneumococal polysaccharide, was synthesized from octaacetyl cellobiose through the intermediate compounds, heptaacetyl bromocellobiose, heptacetyl benzylcellobiose, and benzyl cellobiuronic acid. Preliminary experiments were carried out towards the enzymatic synthesis of Type III polysaccharide by polymerization of the cellobiuronic acid through treatment with an enzyme derived from plants.